According to Martindale’s view, as we drift into sleep we pass through: – waking, problem-oriented thought, – realistic fantasy, – autistic fantasy, – reverie, – hypnagogic (falling asleep) states, and – dreaming.

In altered states of consciousness, the nervous system itself becomes a ‘sixth sense’ that produces a variety of images including entoptic phenomena.

The behaviour of the human nervous system in certain altered states creates the illusion of dissociation from one’s body (less commonly understood in hunting and gathering shamanistic societies as possession by spirits).

San religion is built around belief in a tiered universe. As do other shamanistic peoples throughout the world, the San believe in a realm above and another below the surface of the world on which they live.

There were at least four contexts in which San shamans acquired insights into the spiritual world: – the trance dance, – special curing rituals, – viewing rock art, and – dreams.

The principal aim of a vision quest is to ‘see’ a spirit animal that will become the quester’s animal-helper and source of his power.

Entering a cave” or rock was a metaphor for a shaman’s altered state; therefore, caves (and rocks more generally) were considered entrances or portals to the supernatural world.

Rock art sites were symbolic vaginas, and entry into the wall of a rock art site was thus akin to intercourse.

Sexual arousal and penal erections are associated with both altered states of consciousness and sleep.